The invention concerns an aqueous alkaline bath for the chemical deposition of copper, nickel, cobalt or their alloys, containing compounds of these metals, reducing agent, wetting agent, pH-regulating substance, stabilizer, inhibitor and complex former, and a method for the adhesive chemical deposition of these metals and alloys.
Baths of the above-designated type are generally known. They contain, as a rule, considerable amounts of complex formers, in order to prevent the precipitation of metal hydroxides. This inevitably leads to an unsatisfactory quality of the coating deposited from these baths, which, indeed according to the type of bath, can contain considerable amounts of impurities, such as carbon, nitrogen and hydrogen, among others, which exert a decisive influence on the crystalline structure and thereby on technologically important characteristics such as specific electrical conductivity, interior voltage, adhesive strength, and dilatability, or ductility. The effect is particularly disturbing, for example, with the production of printed circuit boards, during which undesirable bubbles, disengagements and cracks can form, and indeed the more so, the thicker is the deposited metal layer.
The concentrate, or rinse water, accruing upon operation of the known baths, accumulates mainly in the form of solutions, which can be removed from concern only with great technical expenditure, since their direct attribution in the manufacturing process is not possible without more.